Topic: IE7 Arial Displays as Italic?

I was giving one of my sites a visual check and noticed that IE7 was now displaying all the Arial text as italic. On a whim, I checked, and the same thing is true. The style specifies:

font-family: arial, sans-serif;

and it displays as Arial italic. Other support font-families seem to work properly. Has anyone else run across this? Causes? Workarounds?